An image forming apparatus which forms an image with erasable coloring material has already been put into practical use. As the erasable coloring material, coloring material which is made transparent by heating is known. For example, an image forming apparatus can form an erasable full color image with erasable coloring materials of BK (black), C (cyan), M (magenta), Y (yellow).
The image forming apparatus forms an image of toner on a photoconductor drum with erasable coloring material, such as erasable toner. The image forming apparatus primarily transfers the toner image from the photoconductor drum to a transfer belt. The image forming apparatus secondarily transfers the toner image from the transfer belt to a recording medium, such as a sheet. The image forming apparatus fixes the toner image transferred to the sheet by heating by a fixing unit. The fixing unit is temperature controlled so that a heating temperature becomes a fixing temperature within the range from 150 degrees to 180 degrees.
As described above, the heating temperature of the fixing unit is controlled to the fixing temperature within the range of 150 degrees to 180 degrees, but the heating, temperature of the fixing unit may exceed an upper limit temperature of the fixing temperature. For example, being heated by the fixing unit at not less than 190 degrees, the erasable coloring material is made transparent.